Quad-polarization synthetic aperture radar (SAR) satellites are important detection tools in Earth observation and remote sensing; in particular, they are of great significance for accurately interpreting radar data and inverting geophysical parameters. Polarimetric calibration is particularly critical to eliminate the effects of distortion in polarized SAR data. The C-SAR/02 satellite launched by China is an important part of the C-band synthetic aperture radar (SAR) constellation, and the quad-polarization strip I (QPSI) is an important imaging mode for its sea–land observation. The relevant research on its polarimetric calibration is still lacking. This study’s polarimetric calibration of C-SAR/02 was performed based on the active radar calibrator (ARC) method using four independently developed L/S/C multi-band ARCs and several trihedral corner reflectors (CRs). The polarimetric calibration distortion matrix varies along the range direction; the polarimetric calibration distortion matrix and polarimetric calibration accuracy along the range direction were analyzed, incorporating the devices in different range directions to calculate the distortion matrix. This approach improved the accuracy of the polarimetric calibration results and the effect of the quantization application of the C-SAR satellites. Moreover, our experimental results indicate that the method presented herein is suitable for the C-SAR/02 satellite and may also be more universally applicable to C-SAR-series satellites.

Ground deformation monitoring is pivotal for enhancing urban resilience and mitigating geohazards. This study presents a synergistic monitoring framework integrating 26 Sentinel-1A (C-band) and 16 LuTan-1 (L-band) SAR scenes acquired between December 2023 and August 2025 to characterize the deformation dynamics in Beijing. Utilizing SBAS-InSAR, we first established a regional deformation baseline using Sentinel-1A observations, identifying critical subsidence and uplift zones in the eastern plains. Subsequently, high-resolution (3 m) LT-1 data were leveraged to achieve refined spatiotemporal characterization of these deformation hotspots. Validation against ground leveling benchmarks confirmed that both satellites yield high accuracy. LuTan-1 (RMSE = 3.810 mm/a) shows slightly better agreement with the ground leveling data than Sentinel-1A (RMSE = 4.853 mm/a). Analysis of the spatiotemporal patterns derived from InSAR revealed that the study area is characterized by widespread gene uplift (averaging ~10 mm/a), interspersed with acute localized subsidence exceeding 40 mm/a. Correlation analysis demonstrates a high spatiotemporal coupling between the extent and rate of surface uplift and groundwater level recovery. To further investigate these dynamics, Terzaghi’s effective stress principle is employed to quantify the contribution of groundwater level fluctuations to the observed surface deformation. A Parametric Harmonic Model was implemented to decouple elastic and trend components, and attribution analysis confirms that the continuous recovery of groundwater levels is the fundamental driver of the regional surface uplift. The inverted elastic skeletal storativity (S_ke), ranging from 1.587 × 10⁻³ to 9.184 × 10⁻³, reveals that regional surface uplift is predominantly driven by the elastic rebound of aquifer systems following groundwater recovery. In contrast, localized subsidence anomalies observed at large-scale engineering construction sites, landfill facilities, major expressway corridors, and high-density residential areas are independent of groundwater fluctuations, instead they are primarily attributed to anthropogenic stressors. This study elucidates a dual-drive mechanism, which comprising macroscopic hydrogeological rebound and localized anthropogenic disturbance, providing a robust scientific basis for differentiated urban hazard management.

Accurate geometric positioning is essential for the quantitative application of synthetic aperture radar (SAR) imagery. Although geometric calibration can effectively reduce systematic positioning errors, the cross-scene transferability of calibration-derived correction parameters remains insufficiently evaluated, particularly under different acquisition conditions. This study investigates the geometric positioning accuracy and parameter transferability of GF-3B/C SAR imagery using observations from the Xilinhot and Lijiang calibration sites. Scene-specific range and azimuth-time corrections were first estimated within the Range–Doppler framework, followed by cross-scene transfer experiments and acquisition-condition sensitivity analyses. The results indicate that scene-specific correction established a high-accuracy baseline, reducing the median planimetric root-mean-square error (RMSE) from 57.50 m to 1.53 m. In cross-scene transfer, the range correction exhibited substantially higher stability than the azimuth-time correction. Range-only transfer yielded a median combined two-dimensional RMSE of 50.98 m, whereas combined transfer yielded 60.51 m, compared with 57.85 m before transfer. Transfer performance was associated with source–target acquisition compatibility, yielding superior accuracy when satellite platform, orbit direction, and Doppler centroid frequency differences were well matched. Furthermore, cross-site transfer demonstrated accuracy comparable to that of same-site transfer under compatible conditions. These findings indicate that parameter transferability depends on both the specific correction component and acquisition compatibility. For GF-3B/C imagery in ground-control-point-free (GCP-free) scenarios, range corrections offer strong potential for direct reuse, whereas azimuth-time corrections require rigorous compatibility screening during source-scene selection.